Numerous electrical appliances used in commercial and residential environments employ rotary electrical switches which are manually operated by turning, pushing or pulling a control shaft or lever operatively connected to the switch contacts. In assembling the appliances in which such switches are used, it is desirable to shield the switch contact mechanism and the electrical connection to it from the user while permitting access of the user to the control shaft or lever. Such switches are normally mounted by placing the contact mechanism behind a protective plate which normally comprises a surface of the appliance with the control shaft or lever projecting through an aperture in the protective plate. The switch is held affixed to the protective plate with retraction of the control shaft or lever back through the aperture prevented by attaching a fastener to the bushing in which the control shaft is journaled or to the surface of the switch mechanism housing which faces the shielding plate. In some switches of the prior art, the bushing which circumscribes the switch control shaft is threaded to receive a nut with or without a washer which is passed over the shaft from the access side of the plate and threaded onto the bushing to frictionally engage the access surface of the shielding plate. In other switches of the prior art, screw holes are predrilled in the surface of the switch housing adjacent the control shaft or lever and aligning apertures are provided in the shielding plate through which screws may be passed to hold the switch housing in place. Two such screw holes are normally necessary to prevent rotation of the switch housing relative to the shielding plate. Some switch housings utilize one threaded hole to receive a screw and achieve rotational stability through the use of a hook adapted to be received in an eye or slot on or adjacent to the shielding plate.
To enhance insulation and protection from electrical shock, some switches of the prior art utilize plastic components in those portions of the switch housing which come in contact with the shielding plate which is often metal and conductive. The use of screws and nuts with such switch housings results in a tendency for the threads on the plastic bushings or in the holes drilled in the plastic members of the housing to become stripped necessitating that the entire switch assembly be discarded as it is generally not economically feasible to repair such switching devices.
It is also time consuming to align switch mechanisms mounted in housings known to the prior art in proper alignment with fastener holes, eyes or slots and to then thread one or more screws, nuts or washers onto the switch mechanisms to affix them in place.
Another disadvantage of the prior art switches discussed above is that, when used in an environment which is subject to vibration as is commonly the case with electrical apparatus stored in moving vehicles or adjacent motor driven machinery the nuts and screws have a tendency to loosen whereby the switch mechanism can become disengaged from the shielding plate and fall with exposed live wires and contacts against other conducting surfaces, some of which may be energized, thereby resulting in a potentially hazardous condition and, in any event, requiring disassembly of the appliance to restore the switch to its proper position or replace it.